What is the concept of 12x optical zoom?

The ratio of the wide-angle end of the lens to the telephoto end.

12 times optical zoom refers to the ratio of the wide-angle end to the telephoto end of the lens. If the wide-angle end is 30mm and the wide-angle end is 360mm, it is 12 times optical zoom. Digital cameras rely on optical lens structure to achieve zoom. The optical zoom mode of a digital camera is similar to that of a traditional 35mm camera, that is, the scene to be shot is enlarged and reduced by moving the lens.

3 times, 10 times and 12 times optical zoom refer to the ratio of the wide-angle end to the telephoto end of the lens. For example, the wide-angle end is 30mm and the telephoto end is 90mm, which is 3 times optical zoom; If the wide-angle end is 30mm and the telephoto end is 300mm, the optical zoom is 10 times; If the wide-angle end is 30mm and the wide-angle end is 360mm, it is 12 times optical zoom. As for digital zoom, it has nothing to do with the lens, but magnifies the image that the lens can shoot, which has no practical significance, and few people use digital zoom.

Optical zoom is achieved by changing the positions of lens, object and focus. When the image plane moves in the horizontal direction, the visual angle and focal length will change, and the farther scenery will become clearer, making people feel that the object is moving forward.

Obviously, there are two ways to change the perspective. One is to change the focal length of the lens. In photography, this is optical zoom. The focal length of the zoom lens is changed by changing the relative position of the lens. The other is digital zoom. Digital zoom is actually the electronic amplification of the picture, and some pixels on the original CCD image sensor are amplified by interpolation. Enlarge part of the image on the CCD image sensor to the whole picture. Through digital zoom, the shot scene is enlarged, but the image quality will inevitably be lost. In fact, digital zoom does not change the focal length of the lens, but changes the viewing angle by changing the diagonal of the imaging plane, thus producing an effect equivalent to the focal length change of the lens.

Therefore, we can see that some digital cameras with long lenses have more room for moving the internal lens and photoreceptor, so the zoom factor is also larger. We see that some ultra-thin digital cameras on the market generally have no optical zoom function, because the photosensitive devices are not allowed to move inside the fuselage, while digital cameras with "long lens" like Sony F828 and Fuji S7000 all have optical zoom functions of 5, 6 and 7 times. At present, the optical zoom multiple of digital cameras is mostly between 2 and 5 times, which can zoom objects beyond 10 meter to 5-3 meters; There are also some digital cameras whose optical zoom effect is 10 times. The optical zoom factor of home camcorder is 10 ~22 times, and it can clearly shoot things 70 meters away.

The role of optical zoom

In layman's terms, you can choose the composition of the scene you want to shoot by standing still. Scenes are near, far, big and small, and you can easily choose when the zoom changes. Of course, there are other uses, such as telescopic, wide-angle and so on.

It's hard to say how many times is good, because there are many indicators or parameters, depending on your opinion.

For the convenience of taking photos, 3-5 times optical zoom is enough, and it is not used or not used well. Therefore, the current household varieties are basically 3-5 times that of optical zoom.

In addition, if the zoom ratio is large, the resolution will decrease, and professionals will not use lenses with large zoom ratio, preferring to bring more lenses.